Dilution of a Solution
Summary
TLDRIn this educational video, Patti demonstrates the process of preparing a concentrated stock solution of Copper II Sulfate and then diluting it to a known concentration. The three-step procedure includes calculating the required amount of compound, preparing the stock solution, and diluting it. Safety measures like lab coats, safety glasses, and gloves are emphasized. Patti uses 6.2 grams of Copper II Sulfate to create a 0.250-liter, 0.100 M stock solution and then dilutes it to a 0.250-liter, 0.004 M solution. The video covers the use of essential lab equipment and provides a hands-on guide to accurately measuring and mixing solutions.
Takeaways
- 🔬 The video demonstrates the process of preparing a concentrated stock solution and diluting it to a known concentration.
- 📝 The procedure is divided into three parts: calculating the amount of compound needed, preparing the stock solution, and preparing the diluted solution.
- 🧪 The example used is the preparation of a 0.250-liter, 0.100 M copper II sulfate stock solution, followed by diluting it to a 0.250-liter, 0.004 M solution.
- 💼 Safety equipment such as lab coats, safety glasses, and gloves are required for this procedure.
- ⚖️ The calculation for the amount of copper II sulfate pentahydrate needed is pre-completed, and 6.2 grams are required.
- 🔑 Accurate weighing is crucial; the script details how to use a scale to measure out the compound.
- 🌡️ The stock solution is prepared by dissolving the compound in distilled water and then diluting to the mark in a volumetric flask.
- 🏺 The diluted solution is prepared by accurately measuring out a specific volume of the stock solution and adding distilled water to the final volume in a volumetric flask.
- 📏 The script emphasizes the importance of careful measurement and technique to avoid errors, such as not exceeding the meniscus when making up to the mark.
- 🔍 The final step includes sealing the flask with parafilm, inverting to mix, and labeling the flask with the solution's name and concentration.
- 📈 The video concludes with a visual comparison of the stock and diluted solutions, noting the difference in color intensity.
Q & A
What is the purpose of preparing a concentrated stock solution in a laboratory?
-The purpose of preparing a concentrated stock solution is to have a known, high concentration of a compound that can be diluted to various lower concentrations as needed for different experiments or applications.
Why is it necessary to wear a lab coat, safety glasses, and gloves during the preparation of a stock solution?
-Wearing a lab coat, safety glasses, and gloves is necessary to protect the individual from potential hazards such as chemical splashes, inhalation of toxic fumes, and skin contact with chemicals, ensuring safety during the preparation of the stock solution.
What is the molar concentration of the copper II sulfate stock solution being prepared in the script?
-The molar concentration of the copper II sulfate stock solution being prepared is 0.100 moles per liter.
How much copper II sulfate pentahydrate is required to prepare 0.250 liters of a 0.100 M stock solution?
-6.2 grams of copper II sulfate pentahydrate are required to prepare 0.250 liters of a 0.100 M stock solution.
What is the significance of the meniscus when making up a solution to a specific volume in a volumetric flask?
-The meniscus is significant because it represents the curve seen at the top of the liquid in the flask. When making up a solution to a specific volume, the bottom of the meniscus should align with the calibration mark on the flask to ensure the correct volume is achieved.
Why is it important to rinse the weighing boat and funnel after transferring the compound into the volumetric flask?
-Rinsing the weighing boat and funnel after transferring the compound ensures that all the compound is transferred into the volumetric flask, preventing loss and ensuring the accuracy of the solution's concentration.
What is the final concentration of the diluted solution prepared from the copper II sulfate stock solution in the script?
-The final concentration of the diluted solution prepared from the copper II sulfate stock solution is 0.004 moles per liter.
How is the volume of stock solution required for dilution calculated?
-The volume of stock solution required for dilution is calculated using the formula v1 = (c2 * v2) / c1, where c2 is the desired concentration of the diluted solution, v2 is the volume of the diluted solution, and c1 is the concentration of the stock solution.
What is the role of parafilm in the preparation of the stock and diluted solutions?
-Parafilm is used to seal the volumetric flasks after preparation, preventing evaporation and contamination of the solutions, ensuring the stability and accuracy of the solution concentrations.
Why is it important to invert the volumetric flask several times after preparing the stock and diluted solutions?
-Inverting the volumetric flask several times helps to mix the solution thoroughly, ensuring that the solute is evenly distributed throughout the solvent and that the concentration is uniform.
Outlines
🧪 Preparing a Concentrated Stock Solution
In this segment, Patti demonstrates the process of preparing a concentrated stock solution of Copper II Sulfate. The goal is to create a 0.250-liter solution with a concentration of 0.100 molar. Patti outlines the three-part procedure: calculating the amount of compound needed, preparing the stock solution, and diluting it. Safety measures such as wearing a lab coat, safety glasses, and gloves are emphasized. Patti calculates the required 6.2 grams of Copper II Sulfate Pentahydrate and uses a scale, weighing boat, and other lab equipment to measure and mix the compound with distilled water in a volumetric flask. The solution is then dissolved and diluted to the correct volume, ensuring accuracy by observing the meniscus level. The flask is sealed, mixed, and labeled before moving on to the next step.
🌡️ Diluting the Stock Solution
The second part of the video focuses on diluting the prepared stock solution to achieve a more dilute solution with a concentration of 0.004 moles per liter. Patti explains the mathematical calculation required to determine the volume of the stock solution needed for the dilution. Using the formula v1 = c2 × v2 / c1, Patti calculates that 10.0 milliliters of the stock solution is required. She then demonstrates the transfer of the stock solution to an Erlenmeyer flask and the careful measurement using a pipette. The diluted solution is prepared in a 0.250-liter volumetric flask, with distilled water added to reach the correct volume. The flask is sealed, mixed, and labeled, resulting in a lighter-colored solution compared to the stock solution. Patti concludes by encouraging viewers to ask questions and to enjoy the experimental process.
Mindmap
Keywords
💡Stock Solution
💡Dilution
💡Molarity
💡Copper (II) Sulfate Pentahydrate
💡Meniscus
💡Volumetric Flask
💡Pipette
💡Tare
💡Parafilm
💡Graduation Line
Highlights
Introduction to the three-part procedure for preparing a concentrated stock solution and its dilution.
Objective to prepare 0.250 liters of a 0.100 molar copper II sulfate stock solution.
Demonstration of diluting the stock solution to prepare 0.250 liters of a 0.004 molar solution.
Safety measures including lab coat, safety glasses, and gloves are emphasized.
Calculation of 6.2 grams of copper II sulfate pentahydrate needed for the solution.
Use of a scale, weighing dish, and scupula for measuring the compound.
Taring the scale to ensure accurate measurement of the compound.
Transfer of copper II sulfate to a volumetric flask using a funnel to avoid contamination.
Rinsing the weighing boat and funnel with distilled water to transfer all the compound to the flask.
Dissolving the solid by swirling and diluting with distilled water to the mark on the volumetric flask.
Using a disposable pipette to add the last few drops of water to reach the exact volume.
Sealing the flask with parafilm and inverting to mix the solution thoroughly.
Labeling the flask with the name and concentration of the stock solution.
Calculation of the volume of stock solution required for the dilution using the formula.
Preparation of the diluted solution by transferring a measured amount of stock solution to a volumetric flask.
Use of a 10 ml pipette and pipette bulb for accurate transfer of the stock solution.
Adding distilled water to the flask and using a disposable pipette for the final adjustments.
Sealing the diluted solution flask with parafilm and inverting to ensure thorough mixing.
Labeling the diluted solution flask with its concentration and volume.
Visual comparison of the stock and diluted solutions showing the difference in color intensity.
Encouragement for questions and guidance to seek help from instructors or lab assistants.
Transcripts
hi i'm patti today we're going to review
the common procedure and technique for
preparing a concentrated stock solution
then we're going to dilute that stock
solution to a known concentration this
is a three-part procedure part one is
calculating the amount of compound
needed part two is preparing the
concentrated stock solution part 3 is
preparing a diluted solution
for this demonstration we will prepare
0.250 liters of a .100 molar copper ii
sulfate stock solution we will then
dilute the stock solution to prepare
0.250 liter of a
.004 molar solution
for safety purposes a lab coat safety
glasses and gloves are required for this
demonstration let's begin
we need a calculation amount of how much
copper ii sulfate pentahydrate needed to
make the solution i've done the
calculation already and we need 6.2
grams these are the things we're going
to use copper ii sulfate pentahydrate
a scupula
wayne dish
and a scale
first we need to take our copper ii
sulfate and have it ready to start
measuring
put our
weighing dish onto the scale
you will see a value of 2.1 on the scale
we need to tear that which means it
takes away that value and all we'll be
measuring is the product inside the
weighing boat
take the weighing boat off
put your product inside
and place it back on the scale
the reason why we do this step is to
avoid any contamination of the scale or
the product
we have a reading of 4.2 we need to
still add more product
we've reached our value needed 6.2 we
are now ready to make the solution
to complete this step we will use the
following apparatus
100 ml beaker
a volumetric flask
funnel
weighing boat with compound
distilled water
parafilm
disposable pipette
and a marker for labeling
first we will need to pour water into
the volumetric flask until it is about 1
3 full
using a clean dry funnel carefully pour
the compound from the weighing boat into
the volumetric flask
rinse the weighing boat several times
with a small amount of distilled water
from the wash bottle
add the rinse solution to the volumetric
flask with the aid of the funnel
finally rinse the funnel a few times
with water then remove it from the flask
gently swirl the solution until the
solid is dissolved
dilute carefully by adding water from
the 100 ml beaker until the water level
is about one centimeter below the
graduation line on the neck of the flask
use a disposable pipet
to add the last few drops ensuring that
the bottom of the meniscus is at the
graduation line
on this step be careful you don't want
to go over the meniscus line otherwise
you'll have to do it all over again
seal the flask with a small piece of
parafilm
invert the flask several times to ensure
thorough mixing
now label the flask with the name and
concentration of the stock solution
you have now made a stock solution
you can use a stock solution to prepare
a diluted solution
we will now use our stock solution to
prepare
0.250 liters of a diluted solution with
a concentration of 0.004
moles per liter
we will first need to determine the
amount of stock solution required
we want to make a diluted solution with
a concentration of 0.004
moles per liter c2 and a volume of
0.250 liters v2
our stock solution has a concentration
of
0.100 moles per liter c1 the volume of
stock v1 is our unknown quantity to find
the volume of stock required we will
isolate v1 in our equation by dividing
both sides by c1 therefore v1 is equal
to c2 times v2 divided by c1
now substitute in the values of c2 v2
and c1 and solve
the volume of stock required is
0.010 liters or
10.0 milliliters
to prepare the dilution we will need the
following material
stock solution
a 10 ml pipette pipette bulb
erlenmeyer flask
distilled water
disposable pipette
parafilm
and a volumetric flask
here's our stock solution
we do not want to contaminate it by
directly inserting our pipet
so a small amount is first transferred
to an erlenmeyer flask
to use the pipet
place the end in the liquid to be
collected
squeeze the pipet bulb
then securely place over the end of the
pipet
slowly release your grip on the bulb and
allow the liquid to rise up the pipet
you should allow the liquid to rise
above the line marked on the pipet
but stop before the liquid level reaches
the bulb
remove the bulb and quickly cover the
end with your index finger creating a
seal
slowly lift your finger and allow the
liquid to exit until the bottom of the
meniscus is sitting on top of the line
marked on the pipet
if you allow too much to exit simply use
the pipette bulb to draw more liquid in
and try again this takes some practice
so be patient with yourself
once you have the required amount of
liquid pull the pipet out of the
erlenmeyer flask and insert it into a
new
.250 liter volumetric flask
remove your index finger from the end of
the pipet and allow all the liquid to
drain into the flask don't worry if a
few drops remain in the pipet these are
calibrated to deliver the exact amount
of liquid required using the same
procedure as before we now add distilled
water to the flask
monitoring the level and using a
disposable pipette for the last few
drops
once again the bottom of the meniscus
should be sitting on top of the line
marked on the neck of the flask
seal the flask with parafilm
and gently invert to mix thoroughly
label your flask
your diluted solution is now ready for
use
you have now learned how to weigh a
compound prepare a concentrated stock
solution
and prepare a diluted solution
now if you look at them side by side you
can see that
the stock solution is darker
than the diluted solution
if you have any questions about any of
these processes please ask your
instructor or the lab assistant
thanks for watching and happy
experimenting
you
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